High Frequency Chain Inverter Control Based on Topology Decoupling

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Overview:
Based on the topology decoupling idea, a new control strategy for matrix high frequency chain inverter is proposed. According to the polarity of the high frequency loop generated by the high frequency inverter bridge, the topology of the matrix converter is decoupled into two conventional three-phase voltage source inverters, so that the control method of the conventional voltage source inverter can be introduced. In the matrix converter control, the analysis of the matrix converter is simplified. Experimental research has been carried out, and the results show that the control method has better control effect.

0 Preface
DC/AC inverter technology has been widely used in many occasions such as new energy development, AC motor drive, uninterruptible power supply (UPS), and active filter. Although the traditional inverter is mature and reliable, it has the disadvantages of large size, heavy weight, high audio noise, and poor dynamic performance of the system. As the core component of the inverter, the transformer also functions as a transmission power while achieving electrical isolation between the power supply side and the load side. However, since the transmission power is the fundamental wave, the volume and weight of the conventional power frequency transformer used in the inverter are large in the device, which is a major obstacle to improving the power density of the device. The high-frequency chain inverter technology uses high-frequency transformers instead of the traditional power frequency transformers to overcome the above shortcomings and reduce the size and weight of the transformer.
In this paper, a new control strategy is proposed by combining the DC-to-three-phase AC topology and high-frequency chain technology in the matrix converter. The control strategy utilizes a high frequency loop voltage square wave generated by a high frequency inverter bridge operating in a PWM modulation mode to be boosted by a high frequency transformer as an input to a subsequent stage matrix converter. For the post-stage matrix converter, it is decoupled into two conventional voltage source inverters by the idea of ​​“topological decoupling”, so that the control method of the conventional voltage source inverter can be introduced into it, respectively, against the single voltage source. The transformer is controlled. Finally, the high-frequency ring square wave is formed into a unipolar high-frequency pulse by the appropriate switch combination of the power converter of the rear-stage matrix converter, and the low-frequency sine wave of the same frequency as the modulated wave is output through the filter. Combining the PWM control strategy with the high-frequency transformer to form a high-frequency chain and combining it with the matrix converter topology is also the innovation of this paper. The experimental research on the proposed control strategy is carried out. The experimental results verify the feasibility of the control strategy.

1 Circuit topology and control strategy The main circuit topology of DC-to-three-phase AC matrix high-frequency chain inverter is shown in Figure 1. The front stage of the main circuit consists of a single-phase full-bridge circuit and a high-frequency transformer to form a high-frequency inverter bridge, and the latter stage consists of a matrix converter and an output filter circuit. The high-frequency ring square wave generated by the high-frequency inverter bridge is demodulated by the matrix converter, and the higher-order harmonics are filtered by the filter circuit, thereby demodulating the AC pulse voltage of the same frequency as the modulated wave at both ends of the output filter circuit. The control structure block diagram is shown in Figure 2.

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